Sunday / Monday Storm - Latest From The Netweather Team

[Paul]

We'll be online over the weekend and into Monday with updates on the storm - stay tuned to this topic for the latest..

 

Currently a weather watch has been issued here:

http://www.netweather.tv/index.cgi?action=weather-alert-status;sess=

 

And the latest news is here - 'turbo boosted' storm possible

http://www.netweather.tv/index.cgi?action=news;storyid=5478;sess=

[Jo Farrow]

Why might this storm be worse than a usual Autumn Storm? STING JETS

 

There is the possibility for winds to reach severe gale/Storm force over land in a swathe to the south of the Low centre. This may happen over the UK on Monday

After the 1987 storm, forecasting came on leaps and bounds, mainly due to Satellite data and one area of discovery was Sting Jets. 

 

http://www.manchester.ac.uk/aboutus/news/display/?id=9957 (see video)

http://www.metoffice.gov.uk/news/in-depth/1987-great-storm/sting-jet (see PDF at end)

 

This is what can cause the intense damage

Edited October 26, 2013 by Jo Farrow

[Nick F]

There is good agreement now from GFS, UKMO and ECMWF on the track and depth of Monday’s low, though there is still some slight differences on timings of its arrival.

 

Upper-level trough and fast jet stream moving ESE out of NE Canada engaging frontal zone over N Atlantic, which divides warm moist air to the south brought by ex Tropical Storm Lorenzo. A frontal wave develops this evening as a result, with a shallow low forming in the wave under the right entrance of a strong 180mph+ westerly jet streak. GFS slp/jet chart for 18z this evening shows the ‘embryonic’ low in the right entrance of the jet streak

 

 

Air approaching (entering) this region of maximum upper winds is accelerating. This acceleration results in divergence in the upper-level winds in the right half of the entrance region of the jet, resulting in upward motion of air creating winds to converge at the surface and allowing pressure to lower at the surface.

 

The low then deepens quickly over the following 36 hrs of Sunday and Monday morning, the low deepening rapidly Monday morning (pressure falling from circa 974 to 967 mb 00z to 06z) as it comes under the left exit of the next jet streak propagating downstream aloft – where even stronger divergence of air aloft and convergence at the surface will take place.

 

00z GFS was slower with arrival of low across Wales than 00z ECMWF Monday morning, however, the 06z GFS operational seems to have caught up, so the low’s centre is near/over SW Wales at 6am Sunday morning (GFS-972mb and ECM-967mb), the low then tracks NE to be centred over northern England at 9am before exiting to have a centre just offshore over the North Sea by midday. ECMWF deepest at 12z with 962mb, 06z GFS with 969mb. 00z UKMO GM somewhat faster with the low, by 6 hrs but with a very similar track.

 

So still looks like the strongest winds will be across south Wales, southwest and southeast England, The Midlands, Lincs and East Anglia – where we are looking at peak gusts of 70-80mph inland, perhaps 80-90mph along southern coasts – especially across the far southwest. Quite a noticeable squeeze in the isobars towards The Wash and Lincs as the low exits, so some very strong northwest wind gusts here early afternoon.

 

Also, GFS shows 925mb winds of 80knt+ across S England/E Anglia, so potential for these strong winds to lower to the surface as a sting jet on south side of low near back-bent occlusion and cloud head, and also near coastal areas where boundary (surface) layer will likely be unstable with strong winds brought to the surface in downdrafts in any convective cells.

 

Some parts of England and Wales could also see 30mm+ of rainfall, so flooding will also be an issue.

Edited October 26, 2013 by Nick F

[Jo Farrow]

Higher end of the Beaufort scale (over land)

Note Hurricane Force winds are not 'a hurricane'

 

https://forum.netweather.tv/gallery/image/19107-high-end-beaufort-scale-land/

[Jo Farrow]

RAINFALL 

 

Many areas of the UK have already had heavy rain and floods alerts/warnings this week. As a period of stormy weather heads to the UK for the end of this weekend, it is not only the winds which could cause problems.

 

The Environment Agency for England and Wales already has low level alerts out on its 3 day Flood forecast risk page, across all parts.

http://www.environment-agency.gov.uk/homeandleisure/floods/3days/125305.aspx

 

On current forecasts, heavy rain will arrive over Cornwall Sunday evening and will have spread over Wales, the West country, IOW and across to W.Sussex by midnight. By dawn (bit earlier as clocks will have changed) much of England and Wales will have had some heavy rain but it continues over Wales, setting in for North Wales and northern England mid-morning until lunchtime. Only finally clearing away, from NE England, on Monday afternoon. 

 

Sunday night into Monday mid Wales and Dartmoor particularly could see over an inch of rain.

Through into Monday north Wales, Anglesey and NW England could also see over an inch of rain (30mm).

 

So there could be problems with flooding, very tricky conditions on the roads, with standing water, spray and, of course, the gusty gales for Sunday night and during Monday morning.

Edited October 26, 2013 by Jo Farrow

[johnholmes]

Well worth following this link with Jo and Nick. Reliable unbiased outputs as always from them both. 

Edited October 26, 2013 by Paul

[Jo Farrow]

https://forum.netweather.tv/gallery/image/19109-the-bulge-signs-of-the-low/

 

X showing bulge in cloud

Wave forming, low beginning

 

Water vapour image from NOAA 

Edited October 26, 2013 by Jo Farrow

[Paul]

Updated and detailed weather alert now online

http://www.netweather.tv/index.cgi?action=weather-alert-status;sess=

 

[Jo Farrow]

0615Z image from NOAA

 

compare back to 1915Z bulge from last night, image previous post

 

https://forum.netweather.tv/gallery/image/19110-water-vapour-atlantic-06z-27th-oct/

 

[Nick F]

Looks like 00z GFS, ECMWF and UKMO GM have backed off a bit with regards to intensity of the low this morning, EC and UKMO have a shallower and more elongated low which doesn't really see rapid cyclongenesis kick in until it crosses the North Sea, with Denmark and Sweden likely to see worse. GFS looks most shallow with the depression and keeps it as an open wave, which also doesn't deepen rapidly until its over the N Sea when it moves under the developmental left exit region of the jet streak aloft.

 

Nonetheless, think we could still see gusts of 65-75mph along the Channel coast, 55-65mph inland across southern counties of England, 45-55mph north of the M4, 

 

00z GFS fastest with clearance of low, out in the N Sea by 06z, with winds dying down thereafter to a bright, breezy and cool afternoon. Whilst ECM doesn't  exit low from east coast until by 9am. So it looks like strongest winds will blow through by 11am.

 

Still chance that the low may deepen more on next few runs before it crosses/as it crosses the UK than 00z model majority suggest, but definite back off this morning.

Edited October 27, 2013 by Nick F

[Paul]

Storm incoming - be prepared

http://www.netweather.tv/index.cgi?action=news;storyid=5483;sess=

[Paul]

Update from Michael Fish

 

[Jo Farrow]

The worst of the winds, the damaging gusts, looks to be between 00-05Z, midnight and 5am Monday

along the south coast, for Cornwall, and coasts of Devon, Dorset, Hants, IOW, W.+E. Sussex and Kent

Kent continues to see stormy conditions around dawn and the strongest gusts.

 

On current run

Edited October 27, 2013 by Jo Farrow

[Nick F]

12z UKMO, GFS and ECM in agreement with exiting the low into the N Sea around the Wash by 06z Monday, so we are looking at the worst of the winds between 00z and 06z. I think we are looking at winds of 70mph+ along the south coast, gusts 55-65mph inland, though a tight gradient in the isobars is indicated on the SW flank of the low as it exits into the N Sea, so perhaps gusts touching 70mph across E Anglia and SE England 05-06z.

 

These winds aren't as much as the 80-90mph predicted earlier. So this storm is not looking quite as bad as it could have been for the UK. This appears to mainly down to the phasing with the jet, the low doesn't really undego Rapid Cyclogensis (RACY) until its east of the UK over the North Sea. Mid-latitude temperate cyclones tend to undergo RACY when they move to the cold or polar side of the jet stream - which looks to occur east of the UK. Currently the low is just south of the jet stream.

 

The WV imagery from earlier (18z) clearly shows the dark/dry slot which is the jet running from the southwest up across S Ireland and Wales, the mass of cloud or baroclinic leaf hiding the developing low in the warm moist airmass.

 

 

The slp/ jet stream chart for 18z below shows the wave low just south of the jet max core of winds:

 

However, by the time the low reaches Scandinavian west coasts around 15z Monday, its undergoing RACY, as the low has moved on the cold polar side of the jet and is also under the developmental left exit.

 

 

So spare a though for those in Denmark and S Sweden who could be looking at much stronger gusts tomorrow PM.

 

We've perhaps dodged a bullet this time, simply because the low undergoes RACY after leaving the UK. But it will still be very windy and wild tonight/early Monday across southern Britain, with 60-70mph gusts not to be sniffed at. Rain is already looking like to be an issue looking at the radar, 20-30mm possible widely and alot more over high ground.

Edited October 27, 2013 by Nick F

[johnholmes]

thanks for that thoughtful insight into what is happening Nick, also to Jo for her inputs into this area.

Again I recommend folks to read this thread when really interesting and difficult to predict weather is around the UK.

[Paul]

Our weather alert has now been updated:

http://www.netweather.tv/index.cgi?action=weather-alert-status;sess=

 

 

 

 

[Jo Farrow]

https://forum.netweather.tv/gallery/image/19113-eu-meteo-alarm/

 

As the storm clears the east coast of the UK this morning, it will still be deepening over the North Sea 

Meteo alarm, is run by EUMETNET Network of European Met services

Check the website for individual wind warnings for Low countries, Germany and Denmark/Sweden

http://www.meteoalarm.eu/

[Paul]

Jo looks back at the St Jude's day storm

 

http://www.netweather.tv/index.cgi?action=news;storyid=5487;sess=